It has long been desired in the use of forklift clamps to uniformly distribute the loading forces over the entire clamping surface of clamping arms which move together to grip a load, particularly to allow the clamp to handle a plurality of flat sided objects such as rectangular boxes. For example, the arms may be cambered in as in U.S. Pat. No. 2,819,113 to accommodate the deflection of the arms, but has the disadvantage of increasing the effective arm thickness thereby requiring increased operating clearances and is only effective in distributing the clamping forces at a single clamping pressure. Others in attempting to obtain a more uniform gripping pressure have used pivoting pads as in U.S. Pat. No. 2,674,387, or used springs as in U.S. Pat. No. 3,145,866. However, such devices generally require thicker arms thereby desirably increasing the required operating clearances, and are complicated in construction and expensive.
The present invention is directed to clamps for a lift truck in which the arms are generally rigid, single-piece members having generally flat straight outsides and insides and a thin cross section whereby the arms may readily move into and out of small spaces and at least one arm may be pivoted about its inner end inwardly towards the other arm for increasing the equalization of the gripping pressure of the flat insides of the arms from the inner ends to the outer ends of the arms. Furthermore, the arms may be rotated outwardly relative to each other for providing operating clearances between the outer ends of the arms and a load for allowing engaging or disengaging a load. While U.S. Pat. Nos. 2,370,528 and 2,491,805 disclose rotating one or both arms, they will not provide the objectives and advantages of the present device.